The present invention relates to an apparatus and a method of detecting composition of a refrigerant in a refrigerating cycle, and more particularly to an apparatus and a method of detecting composition of mixed-refrigerant circulating in a refrigerating cycle in which the mixed-refrigerant is sealingly filled.
Various methods have been proposed to detect composition of a mixed-refrigerant sealingly filled in a refrigerating cycle.
For example, a heat pump apparatus disclosed in Japanese Patent Unexamined Publication No. 61-138058 comprises a temperature detection portion and a pressure detection portion disposed to detect the temperature and the pressure in the apparatus when the mixed-refrigerant in the apparatus has reached equilibrium by allowing to stand the apparatus for a while after the operation of the heat pump apparatus has been stopped. The method employs a relational graph between temperature and a saturated pressure of the refrigerant which is determined by an internal capacity of the heat pump apparatus, the kinds of the component refrigerants of the mixed-refrigerant, an initial mixture ratio of the mixed-refrigerant and an initial quantity of the enclosed mixed-refrigerant. Then, a saturated pressure at a temperature detected by the temperature detecting portion is calculated. Then, a difference between the saturated pressure and a pressure detected by the pressure detecting portion is calculated to judge a deviation from an initial state of the refrigerant composition. If the deviation is larger than a predetermined value, the mixed-refrigerant is supplemented.
Another prior art for detecting the refrigerant composition has been disclosed in Japanese Patent Unexamined Publication No. 59-129366. In this case, a concentration sensor having a pair of electrodes disposed to face each other with a space therebetween and located in a high-pressure liquid passage arranged from a condenser to an expansion valve are used to detect a capacitance of a flowing refrigerant so that the concentration of the circulating mixed-refrigerant is detected.
Another structure has been prepared in which the composition change in the refrigerating cycle due to leakage of the refrigerant is detected and the result of the detection is fed back to control of the refrigerating cycle. For example, a refrigerating cycle control apparatus for a vehicle disclosed in Japanese Patent Unexamined Publication No. 1-256765 has a refrigerating cycle and opening-degree control means for controlling the degree of opening of expansion valve means so as to make it adequate the degree of superheat of the refrigerant flowing from evaporation means to compression means, and the refrigerating cycle controlling apparatus comprises detection means for detecting a temperature and a pressure of a liquid-phase component flowing from gas-liquid separating means to the expansion valve means, composition ratio judging means for judging the composition in the refrigerating cycle in accordance with the result of detection performed by the detection means, and adjusting means for adjusting a target value of the degree of superheat of the refrigerant to a somewhat larger value in accordance with the result of the judgement. If the composition of the mixed-refrigerant is changed when the mixed-refrigerant outwardly leaks for some reason, the temperature and the pressure of the refrigerant, that are changed in accordance with the foregoing change, are detected from the liquid phase component of the gas-liquid separating means, the composition of the mixed-refrigerant is judged by the composition ratio judging means, the target value of the degree of superheat of the refrigerant is adjusted to a larger value in accordance with the result of the judgement, and the degree of superheat of the refrigerant is controlled by the opening degree control means. Therefore, the cooling performance of the mixed-refrigerant can always be maintained regardless of the leakage of the mixed-refrigerant.
However, each of the foregoing structures detecting the composition of the mixed-refrigerant enclosed in the refrigerating cycle and the refrigerating cycle arranged in such a manner that the composition of the refrigerant is detected and the result of the detection is fed back to control the operation of the refrigerating cycle needs that the refrigerating cycle is stable. Consideration has not been taken to a case where the refrigerating cycle is unstable.
That is, the structure disclosed in Japanese Patent Unexamined Publication No. 61-138051 takes a long time for the refrigerating cycle to be equilibrated, so that the time period during which the refrigerant composition can be detected becomes long. If the refrigerant composition is changed, the operation control must be changed in accordance with the change of the composition. However, the refrigerant composition detected when the operation of the refrigerating cycle is stopped differs from the refrigerant composition in operation of the refrigerating cycle, so that it is not possible to effect a suitable operation thereof. Further, a separate-type air conditioner in which an indoor unit and an outdoor unit are disposed at different places encounters a fact that the temperature conditions for the indoor unit and those for the outdoor unit are different from each other. Therefore, the mixed-refrigerant in the refrigerating cycle cannot be brought to the gas-liquid equilibrium state. As a result, there is a possibility to detect a refrigerant composition different from the actual refrigerant composition.
In the structure disclosed in Japanese Patent Unexamined Publication No. 59-129366, the high pressure passage formed from an Outlet port of the condenser to the expansion valve cannot always be made the superheat liquid state at starting of the refrigerating cycle due to the temperature condition of the place to be air-conditioned or the leakage of the refrigerant or the like. In a case where a gas-liquid phase state is realized, capacitance varies in dependent upon wetness of the refrigerant. Hence, there is a possibility to detect refrigerant composition different from the actual composition of the refrigerant circulating in the refrigerating cycle.
In the structure disclosed in Japanese Patent Unexamined Publication No. 1-256765, because the gas-liquid separating means to detect the refrigerant composition is used, the cost of the refrigerant detection sensor is increased. Further, the level change of the liquid reserved in the gas-liquid separator changes the composition of the refrigerant circulating in the refrigerating cycle. As a result, there arises a problem that the refrigerating cycle becomes unstable.